By DANIEL GOLEMAN

Published: March 22, 1990

Correction Appended

In the first clear evidence that subtle abnormalities in brain structure are associated with schizophrenia, scientists have found differences in brain anatomy between identical twins, one with the disorder and the other normal.

The researchers, at the National Institute of Mental Health, said the findings strongly suggested that even though schizophrenia tended to run in families, factors other than genetics played an important role in the affliction.

The study found that those with schizophrenia, compared with their identical twins, had smaller brain volume, especially in the critical areas involved in thinking, concentration, memory and perception.

The researchers said the findings suggest that ''subtle anatomical changes can be detected in most patients with schizophrenia and are probably characteristic of the disease.''

'Irrefutable Evidence' Seen

The results, being reported today in The New England Journal of Medicine, are ''definitive evidence that schizophrenia is a brain disease and that it involves more than genetic susceptibility,'' said Marsel Mesulam, a neurologist at Harvard Medical School.

The study offers ''irrefutable evidence that schizophrenia is a brain disorder,'' said Lewis L. Judd, director of the National Institute of Mental Health. ''It's a very exciting finding, a landmark study.''

Schizophrenia is marked by distorted thinking and perception of reality, by hallucinations and delusions, as well as by extreme apathy. The disease, which is considered to be the most disabling of mental disorders, afflicts about 2.8 million Americans. While medications can usually control the most flamboyant symptoms of schizophrenia, none cure it.

For decades there has been a debate about whether schizophrenia is a psychological condition brought about by social factors or a disease caused by physical changes in the brain. Although previous studies have shown abnormalities in the brains of schizophrenics, there is such wide variation in the normal brain that many features seen in the brains of schizophrenics are also seen in people without the disease. #15 Sets of Identical Twins The study, at the National Institute of Medical Health's Neurosciences Center at St. Elizabeths Hospital in Washington, involved 15 sets of identical twins recruited through the National Association for the Mentally Ill, an organization of family members of those with schizophrenia.

''Identical twins are the perfect control subjects,'' said E. Fuller Torrey, a psychiatrist who directs the Twin Study Project, of which this research was part. ''You start with two brains that are genetically identical. Without a genetic control, any differences you see may be due to random variation in people's brains.''

The researchers discounted the possibility that the changes they observed in the schizophrenics' brains were secondary results of the disease or its treatment. For example, they said, the changes appeared to be unrelated to the length of time the schizophrenic twins had been ill or the amount of medication they had received.

Using magnetic resonance imaging, a scanning technique that depicts the brain's anatomy in precise detail, the investigators found several striking differences between brains of those who have schizophrenia and those who do not, all suggesting a smaller brain size in schizophrenics.

Strong Differences Found

The differences were so strong that in 12 of the pairs the researchers could identify the twin with schizophrenia just by looking for signs of smaller brain volume in certain areas. No sign of such differences was found in seven sets of normal twins who served as a comparison group.

The most striking difference was that those with schizophrenia had larger ventricles, cavities within the brain that are filled with the same fluid as in the spine. The fluid bathes the brain, both cushioning it and providing nutrients.

''The larger ventricles in those with schizophrenia implies that there is missing tissue somewhere in the brain, and that it has been replaced by cerebrospinal fluid,'' said Richard Suddath, a psychiatrist who was the senior author of the article in The New England Journal of Medicine.

Another difference was that the schizophrenic twins had wider cortical sulci, spaces in the foldings at the surface of the cortex. ''The widening suggests atrophy or a failure of brain cells to develop,'' Dr. Suddath said.

Crucial to Mental Functions

The schizophrenic twins also had a reduction in the size of the left temporal lobe and the front part of the hippocampus, a ridge along each lateral ventricle of the brain. The frontal lobes and hippocampus are crucial to decision making, memory, attention and emotion; schizophrenia involves difficulties with each of these mental functions.

''These patterns have been seen in a hit-or-miss way for almost 15 years,'' Dr. Judd said. ''But in this study with identical twins, you get a clean comparison.''

Depending on what features the scientists were looking for, he said, ''the brain abnormalities are there in 80 to 100 percent of the schizophrenics when you compare them to their twins.''

Because schizophrenia occurs so often in both identical twins (up to 50 percent in some studies), scientists believe that having a genetic susceptiblity is one prerequisite for the condition. In addition, the new findings point to factors other than genetics as contributing to the cause of schizophrenia.

''The results tell you simply that there's been some grief to this brain, but not what, when or where,'' Dr. Mesulam said. ''There's a long list of potential causes, from a viral infection to a trauma leading to an early loss of tissue in neural development.''

Other possiblities under investigation include a slow virus, which remains dormant for much of a person's life but eventually attacks the brain, prenatal oxygen deprivation or difficulties during birth.

''Schizophrenia remains a very mysterious disease, but we're on a sharp ascending limb of discovery of its biological bases,'' Dr. Judd said.

Diagram indicating clues to devastation in the Brain

Correction: March 28, 1990, Wednesday, Late Edition - Final An article on Thursday about schizophrenia misidentified an advocacy group, and an article on Friday about community mental health programs referred to it incorrectly. The organization is the National Alliance for the Mentally Ill; most members are relatives of the mentally ill.